AuthorTopic: GH625-XT - early impressions (Read 3469 times)

I've had my GH615-XT for a couple of weeks now and have done quite a bit of running with it, so I thought I'd jot down a few little things about it. I bought it to replace a GH515B which I'd had for 6 years and which was falling apart and with much reduced battery life. It was time for a replacement, and I was glad not to have to make the leap to a Garmin.

In general, apart from the one serious sporadic problem I mention in another thread, I'm pleased with the watch. It does everything the GH615B did, but probably slightly better - it certainly seems to be quicker to get a satellite fix, and from seeing the route overlaid onto a satellite photo, it does seem remarkably accurate. It looks like battery life will be a lot better too, although I haven't put this to the test yet.

There are, though, a couple of things which I think are slightly problematic:

There is a quirk with the OK button which I've run into a couple of times. When the watch is paused, you can press the OK button lightly, and it makes a little beep, but nothing happens, the timer doesn't start running again. So on a couple of runs I've found that it hasn't recorded a section, because I thought the watch was running when it was still on pause. You have to press the OK button quite firmly to start the timer again. I cannot see what the function of this is. As I see it, when the watch is on pause, any touch of the OK button should start it, and when it's running, any touch of the OK button should pause it. The light press I mentioned is enough to be registered by the watch, hence the little beep, so it should just start or pause the watch (depending on current state). So what's it for? The problem is made a little worse by the fact that the sounds do not seem to convey information in the way they did on the GH615B (or rather 625B, which I upgraded to via firmware). On that watch, when you pressed the OK button to start, you got a little rising 3 note sound, and when stopping, a descending 3 notes - so you could tell what was happening from the sound. The 615-XT seems to have lost this useful little feature.

While the accuracy seems extremely good, I'm convinced the distances are measuring long. I have a regular run I've been doing for a long time, and with the new watch, the beep for the first mile is occurring maybe 20-30 metres sooner than it was with my 625B. This is slightly problematic because the older watch was already seemingly slightly over-optimistic when it came to distance measurement, as in most races it measured the distance as typically 0.5% to 1% further than the official distance. The new one looks as if it will increase this discrepancy, although I haven't yet put it to the test in a race. Something has presumably changed in the distance calculation algorithm, though, and I'd be interested to know what. It's possible that under certain circumstances it's actually more accurate in distance calculation than the 625B, though, because I think that employed a rather over-aggressive smoothing algorithm. I do a lot of running on trails through light woodland, which involves frequent small changes of direction. I believe the 625B tended to over-correct these readings, thinking my zigzag route must be down to slightly erroneous position readings, as these runs tended to measure short (I could see my average pace dropping on the watch, even though I could feel I was keeping the same pace up). When uploaded to SportTracks, these trail runs tended to be measured longer than the watch indicated, presumably because SportTracks employs less aggressive smoothing (and is a little more confident that the readings are accurate).

When I go to save and reset a run (with the ESC button), the message stays on the screen for quite a long time, and it seems I have to wait until it disappears before I can start another run. This goes for other messages as well - they hang around longer than they need to, preventing further action until they disappear. I may be wrong about this and it may be that the watch responds instantly, but it's not clear that it does, and it doesn't inspire confidence. I think it would be a good idea if any key press which would normally result in something being displayed on the screen should do so instantly, replacing whatever is on the screen. If the issue is that it actually takes time to save a track and reset the timer, then it would be a good idea for a warning beep to say that if one attempts to do anything before the watch is ready again.

These little things (and the big thing I mentioned) aside, I think it's a great watch, extraordinary value for money, and I'm glad I stuck with GlobalSat.

...There is a quirk with the OK button which I've run into a couple of times. When the watch is paused, you can press the OK button lightly, and it makes a little beep, but nothing happens, the timer doesn't start running again. So on a couple of runs I've found that it hasn't recorded a section, because I thought the watch was running when it was still on pause. You have to press the OK button quite firmly to start the timer again. I cannot see what the function of this is. As I see it, when the watch is on pause, any touch of the OK button should start it, and when it's running, any touch of the OK button should pause it. The light press I mentioned is enough to be registered by the watch, hence the little beep, so it should just start or pause the watch (depending on current state). So what's it for? The problem is made a little worse by the fact that the sounds do not seem to convey information in the way they did on the GH615B (or rather 625B, which I upgraded to via firmware). On that watch, when you pressed the OK button to start, you got a little rising 3 note sound, and when stopping, a descending 3 notes - so you could tell what was happening from the sound. The 615-XT seems to have lost this useful little feature....

maybe your watch has some button sensitivity issue, but from my experience the beep that allegedly "causes nothing" does something: it quits the Start or Pause message (as long the message appears on the display). If you change the beeper to "message only" the watch only beeps when it actually starts or stops the Activity.

maybe your watch has some button sensitivity issue, but from my experience the beep that allegedly "causes nothing" does something: it quits the Start or Pause message (as long the message appears on the display). If you change the beeper to "message only" the watch only beeps when it actually starts or stops the Activity.

OK, I'll try that out, see if it makes things better. Thanks for the suggestion. It's the beep which makes it confusing. If the beep only occurred as a result of starting or stopping an activity, there wouldn't be an issue.

While the accuracy seems extremely good, I'm convinced the distances are measuring long.

I have found the 625XT to overshoot corners slightly. I compare with a well known competitor that cuts corners. The repeat distance is about the same for the devices though. The competitor reports distances closer to control measured distances despite the 625XT is more true to position.The GPS chip in the 625XT is much better in reacquiring sats. The 625XT hardware is good.

Note that ST and TGP uses the GPS position to determine distances. The device itself uses estimations, probably using the gps accuracy as well. My guess is that the position is trusted too much, the 615 probably have harder filtering. This could be the reason for the too long distances as well as the slightly fluctuating instant pace. I tried to investigate this myself, but cruical information like GPS accuracy display makes this difficult.However, this is "only" device SW and should be possible to do better. GlobalSat has a good track record of improving devices over time, hope this applies here too...

Interesting! I've seen your posts on this subject, gerhard, and you obviously really know your stuff.

I do hope that GlobalSat fine-tune the distance measurement. You could be right that the difference is that they now have greater confidence that the trackpoints recorded are accurate (because of the superiority of the SirfStarIV chipset), and that they can thus 'join the dots' without applying aggressive error correction. Is that what you think is now happening? I'll have to try the watch out on one of my more winding trails, where I could see the average pace dropping with the 615B, and see if the same thing happens with the 625-XT.

I don't know whether this is already possible, as I haven't explored some of the new features of my watch, but it strikes me that it would make very good sense to have activity-dependent error correction. So, if you set the watch to 'Trail Running' or 'Walking', it allows for the fact that the trackpoints may legitimately zigzag, as by the nature of the activity you do often have rapid changes of direction, whereas for a 'Cycling' setting, it would know that as you were going faster and in a straighter line, points recorded far out from that line are probably errors.

Well, after a decent period of usage, I think I have to revise my initial impression of the distance measurement accuracy of the watch. I've run 3 races - 2 10Ks and a 5k. In each case the distance measured was astonishingly close to the official race distance - within a couple of metres. It may just be a coincidence so far, but it certainly inspires confidence.

J2R, Just saw your post but wanted to make a couple of quick comments.

In regards to distance, I have found this unit to be extremely accurate on both trails and road. My training partner has the Garmin 910xt and he and I get almost exactly the same results for distance on both surfaces. I have only ever had one instance where the distance was wayyyy off and that was while running in the Grand Canyon (when you have 4,000 foot canyon walls all around you, I kinda understand this!)

You brought up the issue when you hit the "esc" and the message it gives. This function drives me N&%#!@!@$% in the fact that I **HAVE** to save the data to get it to clear back to 0's (zeroes) on the main display. If I hit "No" to not save the data, it takes me right back to the existing numbers from my workout. There are times when I just want to use the watch as a distance/pace calculator and don't care to save the run. Yes, I get that I can just go in there and delete it, but why not say "delete without saving"?

I'd love a smaller GlobalSat watch with the accuracy of this one with a smaller battery life for my everyday training runs, as I don't really use all the functions of this one in day to day training (ie I just run, no bike/swim). I REALLY love this watch during my longer distance, ultra runs but would love a smaller watch for everyday use that I could train in and wear as a regular watch.